I've not only gone through that, but am actually battling it now. I used to be so full of life, very active, collected things, had hobbies, but in the last five years or so I've simply stopped caring. Hops is right, it IS a sign of depression. The psych I see for my anxiety recommended that I get back into therapy, which I've done. It does help a lot while I'm in her office, but I tend to slide right back into my funk within an hour of leaving. Therapy can sure help, but when the therapist doesn't have much knowledge of NPD, you can only benefit so much. Still, just having someone to talk to is very beneficial. Even though this particular therapist doesn't have much insight into the N-Mother relationship, she listens to me and doesn't judge, so that alone helps to change my outlook. When you're depressed, it's very important to not feel alone.
Some of it may be age, too. I'm at the age (mid 50s) where I no longer think about collecting things, but think about the need to downsize and get rid of all the stuff. When you hit a certain age, the meaning of the word "future" changes, though I'm sure that's something we all go through, and definitely something that counseling can help with.
Please know that you're not alone, and do talk to a professional about it. I can say from my own experience that the longer it goes on, the worse it gets. I'm pretty sure that everyone experiences this kind of funk at some point in their lives. Those of us with baggage definitely have it worse, but there is help out there. You'll be okay.
Hugs,
Kathy